The present invention relates broadly to flexible rubber hoses for low, medium, and, particularly, high pressure applications, and more particularly to a construction therefor for use at low service temperatures.
Flexible rubber hose is used in a variety of hydraulic and other fluid transfer applications for conveying fluid pressures which for “high” pressure applications may range up to about 8000 psi (55 MPa) or more. In basic construction, hoses of the type herein involved typically are formed as having an inner tube or core surrounded by one or more outer layers of a braided or spiral-wound reinforcement material which may be a metal or metal-alloy wire or a natural or synthetic fiber. The reinforcement layers, in turn, are protected by a surrounding outermost jacket or cover which may be of the same or different material as the inner tube. The cover provides the hose with increased abrasion resistance and also helps to protect the hose from being damaged by external forces.
In the case of “rubber,” as opposed to thermoplastic, hose constructions, the inner tube, may be provided as formed of a vulcanizable natural or, more typically, a synthetic rubber material such as Buna-N or Neoprene. Such material or blend may be conventionally extruded and cooled or cured to form the inner tube. As is detailed in U.S. Pat. Nos. 3,116,760; 3,159,183; 3,966,238; and 4,952,262, if necessary, the tube may be cross-head extruded over a mandrel for support, or otherwise supported in later forming operations using air pressure and/or reduced processing temperatures.
From the extruder, the inner tube may be delivered through a braider and/or a spiral winder for its reinforcement with one or more surrounding layers of a wire and/or fibrous material or blend such as a monofilament, yarn, cord, or yarn-wire composite. As is described in Japanese (Kokai) Publ. No. 10-169854 A2, Canadian Patent No. 973,074, and U.S. Pat. Nos. 3,654,967; 3,682,201; 3,790,419; 3,861,973; 3,905,398; 4,007,070; 4,064,913; 4,343,333; and 4,898,212, these reinforcement layers are applied under tension and typically may be formed of an interwoven braid or a spiral winding of a nylon, polyester, polyphenylene benzobisoxazole, polyvinyl acetate, liquid crystal polymer (LCP), or para-, meta-, or other aramid yarn, or a high tensile steel or other metal wire. A bonding or other interlayer of a vulcanizable rubber may be extruded or otherwise applied between each of the reinforcement layers to bond each successive layer to the next layer.
Following the braiding, winding, or other application of the reinforcement layers and the interlayers, an outer cover or sheath optionally may be applied. Such cover, which may be formed as a cross-head extrusion, a moisture-cured or solvent-based dipped coating, or a spiral-wound wrapping, typically comprises an abrasion-resistant synthetic rubber or a thermoplastic such as a polyurethane. Following the application of the cover, the hose construction so-formed is heated to vulcanize the rubber layers and thereby consolidate the construction into an integral hose structure. Representative hose constructions, as well as manufacturing methods and materials therefor, are shown in U.S. Pat. Nos. 3,921,674; 3,953,270; 3,994,761; 4,104,098; 4,238,260; 4,759,388; 6,037,025; 6,474,366 and 7,143,789.
In normal use, such as in mobile or industrial hydraulic applications, hoses of the type herein involved may be exposed to a variety of environmental factors and mechanical stresses which cannot always be predicted. Of utmost importance to the integrity and performance of the hose is that a strong bond is achieved between the constituent parts thereof. However, while it is important to bond these parts together, it is also important that the hose not be made overly stiff so as to make it prone to kinking or fatigue or otherwise unusable for certain applications.
In view of the foregoing, it will be appreciated that hose constructions must exhibit a demanding balance of chemical and physical properties. Indeed, industry standards such as Society of Automotive Engineers (SAE) 100R12, 100R13, and 100R15, International Organization for Standardization (ISO) 3862 Types R12, R13, R15, 4SH, and 4SP, and European Standard EN 856 Types R12, R13, 4SH and 4SP specify a service temperature ranging from −40° C. (−40° F.) to +125° C. (+257° F.). The service pressure for hoses of such types vary by specification and hose diameter, but typically range from 17.5 MPa (2500 psi) to 42.0 MPa (6000 psi).
As commercial applications for hoses continue to increase, it is believed that improvements in hose constructions would be well-received by numerous industries for a variety of mobile and industrial application. Especially desired would be a construction which is flexible and light-weight, and which is resistant to low temperatures so as to meet various industrial standards.